Keeping colors separated, try heating in a pan of water to not quite boiling for a minute, then laying them out on a cookie sheet in the shape they should be and allow them to rest like that for a day or two, preferably two. As a rule the stronger or tougher the plastic is advertised as, and these are supposed to be super tough, the longer the cure time immediately after injecting them….a couple days at least or several hours of cold, like in a fridge.
Plastic will take its permanent “set” during the cure time and will be way more likely to maintain its shape integrity if properly cured. These either were packaged too quickly or they were stored/shipped in an awfully hot environment for long periods of time.